If logging is enabled, but the destination path is not writable, we fall
back to a basic logging configuration. This configuration, however,
doesn't support the parameters we put into the log format string.

We now use our own log formatter unconditionally, and just set up a
StreamHandler if we can't write anywhere.

I hit this when testing against a database with a log path pointing to

a non-existent location. It ended up giving those strange "request_info"

errors we occasionally see. After this change, I had a reasonable console

log.
Unit tests pass.